1. Field of the Invention
This invention is related to the field of computer systems and, more particularly, to data storage systems.
2. Description of the Related Art
Data storage can be expensive. In managing data storage, questions to be asked may include: How much storage does an enterprise need? Does the enterprise have too much storage, or not enough storage? A bias held by many system administrators is to have an excess of storage (more than is really needed) because they typically are not penalized for having too much capital equipment, but may be penalized for running out of storage if, for example, an application has to shut down. So typically, an enterprise may buy more storage than is needed and allocate the storage before it is actually needed to specific applications. This tends to create waste as funds that could be better spent elsewhere in the corporation are unnecessarily tied up in hardware. Reasons for this tendency to acquire too much storage may include that, in the open systems market, it has historically been difficult to add storage quickly. Storage Area Network (SAN) architecture may help with the problem by reducing the amount of time needed between the time that it is determined that more storage is needed and when the new storage is up and available to an application.
In storage systems, utilization is a metric that may be used to decide when an individual file system needs to be resized, but it is not a sufficient metric for understanding storage usage. Utilization, the percentage of storage used in a file system, may have limitations including, but not limited to, the following.
First, utilization typically fails to account for free space available to applications but unavailable to the file system. Commercial databases typically pre-allocate large data files but only use a relatively small portion of the files. Without knowing the rate at which the database consumes these files or the amount of free space available to the database, administrators may have a difficult time measuring storage demand.
Second, as more data is kept, utilization increases. Organizations that keep large amounts of historic data tend to have higher utilization. This does not necessarily imply better inventory management. On a related note, rewarding high utilization may create a disincentive to purge useless data.
The important aspect of storage to be examined, then, is not utilization (how full is the storage? How much are you using at a given time?), but how much storage is being used in relation to the incoming demand. Utilization is not the right metric for analyzing storage levels. Therefore, it is desirable to provide a system and method for applying storage management techniques that deal with demand in storage systems. It is also desirable for these storage management techniques that match storage demand with supply, and to preferably attempt to balance the cost of carrying storage inventory with the cost of running out of storage.